It is known that when delivering a protein and the like into a cell, they can be efficiently introduced by cationizing the protein (patent document 1). In addition, it is known that when a peptidic pharmaceutical such as insulin is used in combination with a cationic macromolecule and the like such as chitosan, promotion of mucosal absorption can be devised without damaging mucosal epithelial cells (non-patent document 1). Additionally, issues on side effects of RNAi treatment that introduce siRNA to a cell by nanoparticles using polycations, and solutions to them were discussed (non-patent document 2). Moreover, in recent years, cationic polymers for being introduced into a cell as a temperature-sensitive fluorescence probe have been reported (patent document 2). However, mechanism of cations inducing the above phenomena, their effects on the cell, and their range of applications, have not necessarily been clarified.
Beside them, a number of works for development of functions focusing on cations have been done. For example, it was found that nano capsules composed of cation-based biopolymer chitosan and γ-glutamic acid have a character that swell/shrink in conjunction with the surrounding pH, and its applications are investigated (non-patent document 3). In addition, a possibility of application of a new type of cation activator to hair conditioners (non-patent document 4), or application of the cationic polymers that have exceptionally low absorption while retaining charge quantity (patent document 3) have been reported.
However, although various cationic polymers can be provided by these technologies, it has been difficult to select polymers that could be easily introduced inside a cell without inhibiting cell proliferation, especially not inhibiting cell division of the cell to which the polymers are introduced.